1. Field of the Invention
The present invention relates to a front substrate of a plasma display panel, and more particularly, to a method for manufacturing a bus electrode of a front substrate of a plasma display panel, using a sheet.
2. Description of the Background Art
FIG. 1 is an exploded perspective view illustrating a conventional plasma display apparatus.
As shown in FIG. 1, the conventional plasma display apparatus is comprised of a front substrate 10 and a rear substrate 20. The front substrate 10 and the rear substrate 20 are spaced apart from each other and attached in parallel.
A plurality of scan electrodes (11_scan) is arrayed to be in parallel with one another on the front substrate 10. The plurality of scan electrodes (11_scan) are comprised of a transparent electrode (or ITO electrode) (11a_scan) that is formed of indium tin oxide (ITO), and a bus electrode (11b_scan), which is on the transparent electrode (11a_scan), that is formed of metal, such as silver (Ag).
A sustain electrode (11_sustain) is paired with the scan electrode (11_scan) and arrayed on the front substrate 10. The sustain electrode (11_sustain) is comprised of a transparent electrode (or ITO electrode)(11a_sustain), and a bus electrode (11b_sustain), which is located in the same way as the scan electrode (11_scan), that is formed of metal, such as silver (Ag),
A dielectric layer 12 limits discharge current, and serves as an insulater between the scan electrode (11_scan) and the sustain electrode (11_sustain).
A protective layer 13 is formed by depositing magnesium oxide (MgO) on the dielectric layer 12, to facilitate emission of secondary electrons and to protect the scan electrode (11_scan) and the sustain electrode (11_sustain).
The rear substrate 20 has stripe-typed (or well-typed) barrier ribs 21 arrayed and maintained in parallel and forming a plurality of discharge spaces, that is, a plurality of cells.
The address electrode 22 is disposed to be in parallel with the barrier rib 21, and performs an address discharge and generates vacuum ultraviolet rays at an intersection of the scan electrode (11_scan) and the sustain electrode (11_sustain).
At the rear substrate 20, red, green, and blue phosphor layers 23 emitting visible rays for image display are coated between the barrier ribs 21, and the dielectric layer 24 is fired and formed on the address electrode 22.
FIG. 2 is a sectional view illustrating another conventional plasma display apparatus.
It is known that a bus electrode comprised of silver (Ag) reflects light incident from the outside and obstructs light resulting from discharge, thereby deteriorating contrast. To solve this problem, a black layer 11c for improving the contrast is formed between a transparent electrode 11a and a bus electrode 11b. Further, a black matrix 14 formed between electrode pairs, absorbs the external light generated from the external of the front substrate 10 and reduces reflection of the external light, thereby improving purity and contrast of the front substrate 10. A reference numeral 12 denotes a dielectric layer.
A method for manufacturing the front substrate 10 of the above-identified conventional plasma display apparatus will be described below.
FIGS. 3A to 3D illustrate the conventional screen printing method used for manufacturing the front substrate of the plasma display apparatus, using a screen printing method.
As shown in FIG. 3A, a black paste 35 for forming the black layer 11c is coated on a screen mask 30, and then the black paste 35 is pushed down using a squeegee 37. The screen mask 30 is comprised of a mesh net 33 generally formed of metal, and a pattern forming layer 31 having a pattern for the black layer 11c. 
If the black paste 35 is pushed down using the squeegee 37, the black paste 35 is moved through a hole 34 in the pattern forming layer 31 of the screen mask 30, thereby forming the black layer 11c on the transparent electrode 11a as shown in FIG. 3B. After the black layer 11c is formed, the black layer 11c is cured in a light curing method using ultraviolet rays or a thermal curing method using heat.
After the black layer 11c has cured, as shown in FIG. 3C, a silver (Ag) paste 39 for forming the bus electrode 11b is coated on the mesh net 33 of the screen mask 30 and then, the silver paste 39 is pushed down using the squeegee 37.
If the silver paste 39 is pushed down using the squeegee 37, the silver paste 39 is moved through the hole 34 provided in the pattern of the pattern forming layer 31 of the screen mask 30, thereby forming the bus electrode 11b on the black layer 11c. After the silver electrode layer 11b is formed, the silver electrode layer 11b is cured in the light curing method using the ultraviolet rays or the thermal curing method using the heat, and the black layer 11c and the silver electrode layer 11b are fired.
The screen mask 30 that is used for forming the electrode of the front substrate 10 through the screen printing method, increases in size as the plasma display panel increases in size. In a case where the electrode is formed through the screen printing method as mentioned above, a curing process needs to be performed after the forming of the electrode and therefore, such need for curing creates an addional complication to the plasma display apparatus manufacturing process that adds significantly to the plasma display apparatus' manufacturing time and cost.
In a case where the electrode is formed through the screen printing method, an additional problem occurs in that it is difficult to more precisely and minutely form the electrode pattern as the plasma display apparatus' resolution increases.